The invention relates to substituted imidazole compounds which inhibit protein kinase enzymes, compositions which contain protein kinase inhibiting compounds and methods of using inhibitors of protein kinase enzymes to treat diseases which are characterized by an overexpression or upregulation of protein kinases. Protein kinases mediate intracellular signal transduction by affecting a phosphoryl transfer from a nucleoside triphosphate to a protein acceptor that is involved in a signaling pathway. There are a number of kinases and pathways through which extracellular and other stimuli cause a variety of cellular responses to occur inside the cell. An extracellular stimulus may affect one or more cellular responses related to cell growth, migration, differentiation, secretion of hormones, activation of transcription factors, muscle contraction, glucose metabolism, control of protein synthesis and regulation of cell cycle.
Many diseases are associated with abnormal cellular responses triggered by protein kinase-mediated events. These diseases include autoimmune diseases, inflammatory diseases, neurological and neurodegenerative diseases, cancer, cardiovascular diseases, allergies and asthma, Alzheimer's disease or hormone-related diseases. Accordingly, there has been a substantial effort in medicinal chemistry to find protein kinase inhibitors that are effective as therapeutic agents.
Serine/threonine kinases are a class of protein kinases that are among the most promising drug targets for future small molecule inhibitors. Inhibition of serine/threonine kinases is likely to have relevance to the treatment of cancer, diabetes and a variety of inflammatory disorders. The successful development of GLEEVEC® as a Bcr/Abl protein kinase inhibitor has provided further evidence that protein kinases are valid drug targets for potential cancer therapies.
Casein kinase 1 (CK1) belongs to the serine/threonine kinase family. In mammals, the enzyme exists in seven isozymic forms: α, β, γ1, γ2, γ3, δ, and ε. By phosphorylating different substrate proteins, these isoforms are able to activate, inactivate, stabilize, or destabilize the functions of the proteins, regulating the functions of various types of different organisms. For example, a tumor suppressor factor p53 and an oncogene mdm2, which are both important proteins for controlling abnormal cell growth, are substrates of casein kinase 1.
Mammalian casein kinase 1δ and casein kinase 1ε are key regulators of diverse cellular growth and survival processes including Wnt signaling, DNA repair and circadian rhythms. They have a kinase domain that is similar to those of other isoforms. However, the N-terminal and C-terminal domains thereof are different from those of other isoforms. The C-terminal domain has a plurality of autophosphorylation sites, and it is considered to be involved in regulation of autoenzyme activity. Phosphorylation of p53 by casein kinase 1δ or casein kinase 1ε leads to a consequent change in the interaction between p53 and mdm2. It has also been known that casein kinase 1ε or casein kinase 1δ is involved in a regulatory protein associated with the formation of a spindle as a central body during cell division, and that the casein kinase 1δ or casein kinase 1ε is involved in apoptosis mediated by TRAIL (tumor necrosis factor-related apoptosis inducing factor) and Fas. It has been further reported that inhibition of casein kinase 1ε or casein kinase 1δ by a nonselective casein kinase 1 inhibitory compound IC261 reduces pancreatic tumor cell growth in vitro and in vivo (Brockschmidt et al., Gut, 57(6):799-806 (2008)). Hence, a medicament inhibiting the function of casein kinase 16 or casein kinase 1ε would be expected to exert important phenotypic and therapeutic effects broadly in development and disease, especially cancer.
The present invention relates to a new class substituted imidazoles found to be effective in inhibiting casein kinase 1δ or casein kinase 1ε. These novel compounds are provided to be useful as pharmaceuticals with desirable stability, bioavailability, therapeutic index and toxicity values that are important to their drugability.